Miniature x-ray source

Abstract

An x-ray head according to the invention includes an evacuated chamber in which a cathode and an anode are disposed and electrical connections from the anode and cathode extending through the wall of the evacuated chamber. The cathode may include a gated array of field emission elements, an array of solid state miniature thermionic cathodes, or ferroelectric cathodes. The anode is a metal producing x-ray radiation in response to the impact of electrons produced by the cathode. The anode may be a foil, a thin film of metal deposited on the inside surface of a wall of the evacuated chamber, or a self-supporting body of a metal that produces x-rays in response to electron impacts. The wiring may include conventional pins penetrating through and sealed to the wall of the chamber for connection to a flexible cable.

We claim: 
     
       1. An x-ray source including: a head comprising an evacuated envelope having an outer wall and containing an anode made of a metal producing x-rays in response to the impact of electrons, a cathode including an array of cathode elements respectively producing electrons accelerated toward the anode in response to an electric field between the anode and the cathode elements, the cathode not exceeding ten centimeters in maximum dimension so that the x-ray source can be inserted into a cavity of the human body, the anode being spaced sufficiently far from the cathode for applying an accelerating voltage between the cathode and the anode without voltage break-down and producing x-rays of wavelengths suitable for diagnosis and treatment of a human, and a gate electrode for controlling the flow of electrons from the cathode to the anode; and   respective electrical leads extending from the anode and the cathode and out of the envelope.   
     
     
       2. The x-ray source of claim 1 wherein each of the cathode elements is a field emission cathode producing electrons in response to an electric field. 
     
     
       3. The x-ray source of claim 1 wherein each of the cathode elements is a thin film thermionic cathode element including a metal film directly heated by a current flowing through the metal film for emitting electrons. 
     
     
       4. The x-ray source of claim 1 wherein the anode includes a metal body having a generally planar surface directed toward the cathode and oblique to a direction along which electrons are emitted from the cathode. 
     
     
       5. The x-ray source of claim 1 wherein each of the cathode elements is a ferroelectric cathode element producing electrons in response to a pulsed electrical signal. 
     
     
       6. The x-ray source of claim 1 wherein the anode is disposed opposite only part of the envelope. 
     
     
       7. The x-ray source of claim 1 wherein the anode is a metal foil. 
     
     
       8. The x-ray source of claim 1 wherein the anode is a metal film deposited on the envelope. 
     
     
       9. The x-ray source of claim 1 wherein the anode includes a metal body having a generally conical surface pointed toward the cathode and aligned with a direction along which the cathode emits electrons. 
     
     
       10. The x-ray source of claim 1 wherein the evacuated envelope has an outer wall including a generally planar portion on which the anode is disposed and a collimating element disposed adjacent the planar portion of the envelope for collimating x-ray radiation produced at the anode. 
     
     
       11. The x-ray source of claim 10 wherein the collimating element is a metal that absorbs x-rays and includes a plurality of aligned holes for passage of x-rays that are not incident on the collimating element. 
     
     
       12. The x-ray source of claim 10 wherein the collimating element is disposed outside the envelope adjacent the planar portion of the envelope.